linux-kernel - Re: [RFC][PATCH] PM / Hibernate: Add sysfs knob to control size of memory for drivers

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Message-ID: <20110518172717.GA5734@elf.ucw.cz>
Date:	Wed, 18 May 2011 19:27:17 +0200
From:	Pavel Machek <pavel@....cz>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Linux PM mailing list <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Martin Steigerwald <Martin@...htvoll.de>
Subject: Re: [RFC][PATCH] PM / Hibernate: Add sysfs knob to control size of
 memory for drivers

Hi!

> > From: Rafael J. Wysocki <rjw@...k.pl>
> > 
> > Martin reports that on his system hibernation occasionally fails due
> > to the lack of memory, because the radeon driver apparently allocates
> > too much of it during the device freeze stage.  It turns out that the
> > amount of memory allocated by radeon during hibernation (and
> > presumably during system suspend too) depends on the utilization of
> > the GPU (e.g. hibernating while there are two KDE 4 sessions with
> > compositing enabled causes radeon to allocate more memory than for
> > one KDE 4 session).
> > 
> > In principle it should be possible to use image_size to make the
> > memory preallocation mechanism free enough memory for the radeon
> > driver, but in practice it is not easy to guess the right value
> > because of the way the preallocation code uses image_size.  For this
> > reason, it seems reasonable to allow users to control the amount of
> > memory reserved for driver allocations made after the preallocation,
> > which currently is constant and amounts to 1 MB.
> > 
> > Introduce a new sysfs file, /sys/power/reserved_size, whose value
> > will be used as the amount of memory to reserve for the
> > post-preallocation reservations made by device drivers, in bytes.
> > For backwards compatibility, set its default (and initial) value to
> > the currently used number (1 MB).
> > 
> > References: https://bugzilla.kernel.org/show_bug.cgi?id=34102
> > Reported-by: Martin Steigerwald <Martin@...htvoll.de>
> > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> 
> OK, there are no comments, so my understanding is that everyone is fine
> with this patch and I can add it to my linux-next branch.

Actually no, I don't like it. Yes, knob might be useful for debugging,
but having it as part of official kernel interface...

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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